Engines, such as spark ignition engines, compression ignition dual fuel engines, and so on, employ a fuel such as Liquefied Natural Gas (LNG) for combustion. Such engines depend on a pressure within a fuel/LNG tank thereof to provide adequate flow of the fuel in order to eliminate a need for an additional fuel/cryogenic pump.
During refueling of the LNG tank, a temperature of the LNG tank may reduce mainly due to low temperature of an incoming supply of the LNG. As a result, a pressure within the LNG tank may be reduced proportionately. Also, during operation of the engine, as the LNG is consumed, a volume of the LNG within the LNG tank may reduce in turn resulting in a drop in the pressure within the LNG tank. In such situations, the pressure of the fuel supplied to the engine may be reduced below a specified threshold resulting in reduced or undesirable performance of the engine.
U.S. Pat. No. 6,125,637 describes a fuel delivery system having a fuel tank configured to receive liquid natural gas. The system includes a first conduit extending from a vapor holding portion of the fuel tank to an economizer valve. The system includes a second conduit extending from a liquid holding portion of the fuel tank to the economizer valve. The system includes a vaporizer coupled to the economizer valve. The vaporizer is heated by a coolant from an engine and is positioned below the fuel tank. The economizer valve selectively withdraws either liquid natural gas or vaporized natural gas from the fuel tank depending on a pressure within the vapor holding portion of the fuel tank. The system also includes a delivery conduit extending from the vaporizer to the engine. The system further includes a return conduit having a check valve formed therein extending from the delivery conduit to the vapor holding portion of the fuel tank for pressurizing the fuel tank.